WhiteSur-gtk-theme/src/sass/gnome-shell/widgets-40-0/_dash.scss

$dash_background_color: rgba(white, 0.15);
$dash_placeholder_size: 32px;
$dash_padding: $base_padding + 4px; // 10px/8px
$dash_spacing: $base_padding / 4;
$dash_bottom_margin: $base_margin * 4;
$dash_border_radius: $dash_padding * 1.5 + 12px;

#dash {
  margin-top: $base_spacing * 2;
  padding: 0;

  .placeholder {
    background-image:none;
    background-size: contain;
    height: $dash_placeholder_size;
  }

  // Running app indicator (shown in dash)
  .app-well-app-running-dot {
    margin-bottom: 0;
  }

  .dash-background {
    background-color: $dash_background_color;
    margin-bottom: $dash_bottom_margin;
    padding: $dash_padding $dash_padding - $dash_spacing * 2;
    border-radius: $dash_border_radius;
  }

  // Dash Items
  .dash-item-container {
    margin: 0 $dash_spacing;

    > * { margin: 0; }

    .app-well-app, .show-apps {
      padding: $dash_padding $dash_spacing $dash_padding + $dash_bottom_margin;
    }

    .overview-icon {
      padding: $dash_padding / 2;
      border-radius: $dash_padding / 2 + 12px;
    }
  }

  .dash-separator {
    width: 1px;
    margin: 0 ($dash_spacing + ($dash_padding / 2)) $dash_bottom_margin;
    background-color: rgba(white, 0.25);
  }
}